docs: def plotBrokerQueue(dataTask, filename):
      """Generates the broker queue length graphic."""
      print("Plotting broker queue length for {0}.".format(filename))
      plt.figure()
  
      # Queue length
      plt.subplot(211)
      for fichier, vals in dataTask.items():
          if type(vals) == list:
              timestamps = list(map(datetime.fromtimestamp, map(int, list(zip(*vals))[0])))
              # Data is from broker
              plt.plot_date(timestamps, list(zip(*vals))[2],
                            linewidth=1.0,
                            marker='o',
                            markersize=2,
                            label=fichier)
      plt.title('Broker queue length')
      plt.ylabel('Tasks')
  
      # Requests received
      plt.subplot(212)
      for fichier, vals in dataTask.items():
          if type(vals) == list:
              timestamps = list(map(datetime.fromtimestamp, map(int, list(zip(*vals))[0])))
              # Data is from broker
              plt.plot_date(timestamps, list(zip(*vals))[3],
                            linewidth=1.0,
                            marker='o',
                            markersize=2,
                            label=fichier)
      plt.title('Broker pending requests')
      plt.xlabel('time (s)')
      plt.ylabel('Requests')
  
      plt.savefig(filename)